Micromachined fluidic device and method for making same

ABSTRACT

The fluid-flow device ( 100 ) of the invention comprises a stack ( 30 ) covered by a closure wafer ( 20 ), said stack ( 30 ) comprising a support wafer ( 36 ), a layer of insulating material ( 34 ), and a silicon layer ( 32 ). The closure wafer ( 20 ) and/or said silicon layer ( 32 ) are machined so as to define a cavity ( 38 ) between said closure wafer ( 20 ) and said silicon layer ( 32 ), said support wafer ( 36 ) has at least one duct ( 102 ) passing right through it, said layer of insulating material ( 34 ) presenting at least one zone ( 35 ) that is entirely free of material placed at least in line with said duct ( 102 ) so as to co-operate with said cavity ( 38 ) to define a moving member ( 40 ) in said silicon layer ( 32 ), the moving member being suitable under the pressure of liquid in said cavity ( 38 ) for reversibly moving towards said support wafer ( 36 ) until contact is made between said moving member ( 40 ) and said support wafer ( 36 ).

The invention relates to a fluid-flow device and to its method ofmanufacture. The invention also relates to particular forms offluid-flow device constituting a member for controlling liquid inlet,e.g. forming a non-return check valve, or a member for detecting liquidpressure.

The present invention also relates to a micropump constituting afluid-flow device, and particularly but not exclusively forming amicropump for medical use for delivering a controlled quantity of aliquid medicine on a regular basis.

The manufacture of such fluid-flow devices, and in particular suchmicropumps is based on technologies for micromachining silicon or anyother micromachinable material, in particular using photolithographictechniques with chemical etching, laser ablation, microreplication, etc.

For the particular above-specified application, and also in other cases,it is necessary to provide an inlet control member that allows themicropump to be self-priming. The micropump is driven by varying thevolume of the pump chamber (alternately reducing it and increasing it),e.g. by delivering drive from a piezoelectric actuator.

The European patent application published under the No. 0 453 532describes such a micropump. Nevertheless, such a micropump does notprovide its own self-priming since it presents large dead volumes, thesevolumes contributing to degrading the compression ratio achieved by themicropump.

In order to improve that aspect, a novel micropump has been developed,such as that described in the international patent application publishedunder the No. WO 99/09321. In order to minimize dead volumes and inparticular dead volumes downstream from the seat of the inlet valve, aninlet valve is provided in that pump that is thick in that said inletvalve constitutes the entire thickness of an intermediate wafer (orintermediate plate), the seat of the valve being situated on its sideopposite from the moving diaphragm (or membrane). Nevertheless, such amicropump is complex in structure, difficult to manufacture, and stillhas dead volumes that are large.

An object of the present invention is to provide a fluid-flow device,e.g. a member for controlling liquid inlet or a member for detectingliquid pressure or a micropump, capable of being manufactured insimplified manner and constituting a fluid-flow device that is madereliable in its operation by minimizing dead volumes.

To this end, the invention provides a fluid-flow device comprising astack covered by a closure wafer (or closure plate), said stackcomprising a support wafer (or support plate), a layer of insulatingmaterial covering at least part of said support wafer, and a layer ofsingle-crystal or polycrystalline silicon covering said layer ofinsulating material and covered by said closure wafer, said closurewafer and/or said silicon layer being machined so as to define betweensaid closure wafer and said silicon layer a cavity to be filled withliquid, said support wafer having at least one duct passing rightthrough it, and said layer of insulating material having at least onezone that is entirely free from material placed at least in line withsaid duct so as to co-operate with said cavity to define a moving memberin said silicon layer that responds to pressure of the liquid in saidcavity by moving reversibly towards said support wafer. In a first typeof fluid-flow device, said moving member moves reversibly towards saidsupport wafer until making contact between said moving member and saidsupport wafer.

According to preferred characteristics:

-   -   said support wafer is made of silicon, of quartz, or of        sapphire, and presents thickness lying in the range 50        micrometers (μm) to 1 millimeter (mm), and preferably in the        range 300 μm to 500 μm;    -   said layer of insulating material is of thickness lying in the        range 100 nanometers (nm) to 2 μm, and preferably in the range        0.5 μm to 1 μm;    -   said closure wafer is made of glass or of silicon, preferably        single-crystal silicon; and    -   said layer of silicon is made of single-crystal or        polycrystalline silicon and presents thickness lying in the        range 1 μm to 100 μm, and preferably in the range 10 μm to 50        μm.

In another aspect, the present invention provides a method ofmanufacturing a fluid-flow device of the above-specified type, themethod being characterized in that it comprises the following steps:

-   -   providing a stack comprising a support wafer, a layer of        insulating material, preferably made of silicon oxide, covering        at least part of said support wafer, and a layer of        single-crystal or polycrystalline silicon covering said layer of        insulating material and presenting a free face;    -   using photolithography and chemical etching to machine said        cavity from said closure wafer and/or from the free face of said        silicon layer;    -   using photolithography and chemical etching to machine at least        one duct passing right through said support wafer;    -   chemically etching said layer of insulating material at least        via said duct such that a zone of said silicon layer is freed        from said layer of insulating material, thereby forming said        moving member;    -   providing at least one closure wafer; and    -   using a physicochemical method, preferably by wafer bonding, to        connect said closure wafer in leaktight manner to said surface        of silicon layer that has not been machined.

Thus, in the present invention, it is preferable to use a stackcomprising a silicon support wafer covered in a layer of silicon oxide,itself covered in a layer of silicon. The stack is commerciallyavailable and is conventionally referred to as silicon-on-insulator(SOI).

The use of this type of stack makes it possible to obtain a fluid-flowdevice presenting thicknesses that are constant and under strictcontrol, while nevertheless implementing a method of manufacture that issimple.

In particular, this method of manufacture is considerably simpler toimplement than the method described in the international patentapplication published under No. WO 98/14704.

The various portions of the fluid-flow device are made by selectivechemical etching from both sides of the stack, i.e. from both faces ofthe wafer constituting said stack: the layer of insulating material(made of silicon oxide in an SOI stack) forms a stop or a barrieragainst etching during micromachining of the support wafer or of thesilicon layer.

In addition, the closure wafer, which serves to close in particular thecavity made in the machined silicon layer, is itself preferably made ofglass or of single-crystal silicon.

When the closure wafer is made of glass, it is fixed to the layer ofsilicon in a manner that is known per se, using the technique of anodicbonding.

When the closure wafer is made of silicon, it is fixed to the siliconlayer using the known direct Si—Si bonding technique.

In a first aspect of the fluid-flow device of the invention, there isprovided a liquid inlet control member forming a non-return check valve,the member comprising a stack covered in a closure wafer, said stackcomprising a support wafer, preferably made of silicon, a layer ofinsulating material, preferably made of silicon oxide, covering at leastpart of said support wafer, and a layer of single-crystal orpolycrystalline silicon covering said layer of insulating material andcovered by said closure wafer, said closure wafer and/or said siliconlayer being machined so as to define a cavity between said closure waferand said silicon layer, said cavity being designed to be filled withliquid and presenting at least one gap (or clearance hole) machined inthe entire thickness of the silicon layer, said support wafer having atleast one liquid inlet duct passing right through it and situated atleast in register with (facing) said cavity, and said layer ofinsulating material having at least one zone entirely free of materialextending at least in line with said duct and said gap so as toco-operate with said cavity to define a moving member in said siliconlayer to form a flap for said valve, a portion of said silicon layersurrounding said moving member presenting elasticity making it possiblein the event of a difference in liquid pressure between said liquidinlet duct and said cavity to allow said moving member to movereversibly towards said support wafer.

In this first type of fluid-flow device, said liquid inlet duct of theliquid inlet control member defined in the preceding paragraph issituated close to but not in register with said gap, and said movingmember moves between a closed position in which the moving member is inleaktight contact against said support wafer which forms a seat for saidvalve at least around said duct, liquid flow being prevented betweensaid liquid inlet duct and the cavity, and an open position of the valvein which the moving member is no longer in leaktight contact against thesupport wafer around said duct, in which the moving member allows liquidflow from said liquid inlet duct towards said gap.

In a second aspect of the fluid-flow device of the present invention,there is provided a liquid pressure detection member comprising a stackcovering a closure wafer, said stack comprising a support wafer,preferably made of silicon, a layer of insulating material, preferablymade of silicon oxide, covering at least part of said support wafer, anda layer of single-crystal or polycrystalline silicon covering said layerof insulating material and covered by said closure wafer, said closurewafer and/or said silicon layer being machined so as to define a cavityfor filling with liquid between said closure wafer and said siliconlayer, said support wafer having as least one duct passing right throughit and situated in register with (facing) said cavity, and said layer ofinsulating material having at least one zone that is entirely free ofmaterial placed at least in line with said duct so as to co-operate withsaid cavity to define a moving member in said layer of silicon, saidsilicon support wafer presenting a portion in register with (facing) themoving member forming an island that is separated from the remainder ofthe support wafer by said duct, said moving member being capable, byvirtue of its elasticity and under pressure of liquid in said cavity, ofmoving reversibly towards the support wafer.

In the first type of fluid-flow device, said moving member of the liquidpressure detection member as defined in the preceding paragraph iscapable of going from an open position to a closed position in which themoving member is in physical contact with said portion situated facingthe moving member forming an island that is separated from the remainderof the support wafer by said duct and which forms a bearing portion ofthe silicon wafer, said physical contact being electrically detectable.

In a third aspect of the fluid-flow device of the present invention,there is also provided a micropump comprising a stack covered in aclosure wafer, said stack comprising a support wafer, preferably made ofsilicon, a layer of insulating material, preferably made of siliconoxide, covering at least part of said support wafer, and a layer ofsingle-crystal or polycrystalline silicon covering said layer ofinsulating material and covered by said closure wafer, said closurewafer and/or said silicon layer being machined so as to define a cavitybetween said closure wafer and said silicon layer, the cavity being forfilling with liquid and including a pump chamber, said support wafercomprising at least a first duct passing right through it and situatedin register with (facing) said cavity, said layer of insulating materialhaving at least one first zone that is entirely free of material placedat least in line with said first duct so as to co-operate with saidcavity to define a first moving member in said silicon layer, the firstmoving member being suitable under pressure of liquid in said pumpchamber for moving reversibly towards said support wafer, said firstmoving member forming part of the flap of a liquid inlet control member,and said micropump further comprising a pumping portion comprisingcontrol means fitted with a pump diaphragm to cause the volume of thepump chamber to vary periodically, and liquid outlet control means.

In the first type of fluid-flow device, the first moving member of theliquid inlet control member defined in the preceding paragraph issuitable, under the pressure of the liquid in said pump chamber, forcoming into leaktight contact against said support wafer, said firstmoving member constituting the flap of said liquid inlet control member.

In preferred manner, said micropump further comprises a second zone, inthe layer of insulating material, that is entirely free of materialwhich co-operates with said cavity to define a second moving member insaid silicon layer, the second moving member being suitable under thepressure of liquid in said pump chamber for moving towards said supportwafer, said second moving member constituting the flap of a liquidoutlet control member.

Thus, the present invention relates to various types of fluid-flowdevice which, in accordance with the essential characteristic of thepresent invention, are made form a stack of the SOI type, i.e.comprising a support wafer that is preferably made of silicon, coveredin layer of insulating material, preferably silicon oxide, itselfcovered in a layer of silicon.

Thus, contrary to prior art fluid-flow devices and micropumps for whichit is necessary to perform machining throughout the thickness of asilicon wafer that is to form the intermediate wafer between two wafersof glass, the present invention proposes using a stack in which theinitial thicknesses of the three components (support wafer, layer ofinsulating material, and silicon layer) serve firstly to ensure that thevarious portions of the fluid-flow device are of well-controlledthickness, and secondly that the dead volumes are very considerablyreduced compared with the prior art.

Another major advantage of the technology of the present invention liesin the manufacturing method being simplified compared with thetechniques of the prior art.

The invention will be better understood and secondary characteristicsand advantages thereof will appear on reading the following descriptionof various embodiments of the invention given by way of example.

Naturally the description and the drawings are given purely by way ofnon-limiting indication.

Reference is made to the accompanying drawings, in which:

FIG. 1 is a cross-section through a liquid inlet control member,constituting a first aspect of a fluid-flow device of the presentinvention, implementing a first embodiment thereof;

FIGS. 1A and 1B are plan views of two variants of the FIG. 1 liquidinlet control member, the closure wafer covering the stack beingremoved;

FIGS. 2, 2A, and 2B are views similar to those of FIGS. 1, 1A, and 1B,showing a second embodiment of the first aspect of a fluid-flow deviceof the present invention;

FIGS. 3 and 3A are views similar to FIGS. 1 and 1A showing a thirdembodiment of the first aspect of a fluid-flow device of the presentinvention;

FIGS. 4 and 4A are views similar to FIGS. 1 and 1A showing a fourthembodiment of the first aspect of a fluid-flow device of the presentinvention;

FIG. 5 is a cross-section through a liquid pressure detectorconstituting a second aspect of a fluid-flow device of the presentinvention;

FIGS. 5A and 5B are plan views of two variant embodiments of the FIG. 5liquid pressure detector, the closure wafer covering the stack and thesilicon layer being removed;

FIG. 6 is a view similar to FIG. 5 showing a second embodiment of thesecond aspect of a fluid-flow device of the present invention;

FIG. 7 is a longitudinal section view, partially in perspective, of amicropump constituting a third aspect of a fluid-flow device of thepresent invention;

FIG. 8 is a diagrammatic longitudinal section view of the FIG. 7micropump;

FIG. 9 is a plan view of the micropump of FIGS. 7 and 8, the closurewafer covering the stack being removed;

FIGS. 10 to 15 show various steps in the manufacture of the pump ofFIGS. 7 and 8;

FIG. 16A is a plan view of a variant embodiment of the pumping portionof FIGS. 7 to 9, forming a plurality of liquid pressure detectors, theclosure wafer covering the stack and the silicon layer being removed;

FIG. 16B is a view similar to FIG. 16A showing another variantembodiment of the pumping portion of FIGS. 7 to 9, forming a liquidpressure detector of angular shape;

FIG. 17 is a view on a larger scale of the liquid outlet control memberof the micropump of FIGS. 7 and 8; and

FIG. 18 shows a variant embodiment of the liquid outlet control memberof FIG. 17.

Throughout the figures, when the same element is shown in a plurality offigures it is always given the same numerical reference.

In addition, for reasons of clarity, it should be understood that thethickness of the various elements shown are exaggerated to a very greatextent in the drawings so that the drawings are not strictly to scale.

In a first aspect of the fluid-flow device of the present invention, thefluid-flow device forms a liquid inlet control member and an embodimentthereof is shown in FIG. 1. This liquid inlet control member 100 forconstituting a one-way valve or check valve (non-return valve) comprisesa glass closure wafer 20 placed on top of a stack 30 that has previouslybeen machined in order to form the various functional portions of saidcontrol member 100.

The stack 30 comprises a silicon layer 32 surmounting a silicon oxidelayer 34, itself placed on a silicon support wafer 36.

This type of stack is commonly referred to as a silicon-on-insulator(SOI) stack and is commercially available in the form of wafers orplates suitable for use in the semiconductor electronics industry. Theroles of these three elements in the stack 30 determine thicknesses thatare significantly different:

-   -   the silicon support wafer 36 acting as a rigid base preferably        has thickness lying in the range 50 μm to 1000 μm, and        advantageously in the range 300 μm to 500 μm;    -   the silicon oxide layer 34 serves to connect the silicon support        wafer 36 to the silicon layer 32 while maintaining a constant        spacing between them, and while also being easy to remove in        certain zones so its thickness should remain very small,        preferably lying in the range 0.1 μm to 2 μm, and advantageously        in the range 0.5 μm to 1 μm; and    -   the silicon layer 32 is designed to be machined throughout its        thickness to form liquid passages or through a fraction only of        its thickness (about half) so as to co-operate with the glass        closure wafer 20 to define a cavity, and in some cases a moving        member; this silicon layer 32 which may be made of        single-crystal or polycrystalline silicon, presents initial        thickness that lies preferably in the range 1 μm to 100 μm, and        advantageously in the range 10 μm to 50 μm.

The stack 30 is machined by conventional techniques of photolithographyand chemical etching in order to obtain the various functional elementsof the inlet control member 100, in particular a cavity 38 and a movingmember 40, prior to connecting the glass closure wafer 20 with saidstack 30. This connection between the closure wafer 20 and the free faceof the silicon layer 32 is performed in known manner by wafer bonding(anodic bonding when the closure wafer is made of glass) serving toproduce fixing that constitutes a leaktight connection.

A liquid inlet duct 102 passes through the silicon support wafer goingright through its entire thickness from a first end 102 a to a secondend 102 b. The second end 102 b is adjacent to a circular zone 35 of thesilicon oxide layer 34 that is completely free from material and thatextends well beyond the liquid inlet duct 102.

The silicon layer 32 has been machined through a fraction of itsthickness on its side remote from the silicon support wafer 36 so as toform the cavity 38. In addition, a gap 104 (or clearance hole)corresponding to the entire thickness of the silicon layer 32 beingremoved is situated in line with the cavity 38 and the zone 35 having nosilicon oxide, close to but not directly in register with (facing) thesecond end 102 b of the liquid inlet duct 102 which faces towards thesilicon oxide layer 34.

The cavity 38 extends in register with at least said zone 35 and theliquid inlet duct 102.

In this manner, as can be seen more clearly in FIGS. 1A and 1B, there isformed a member 40 in the silicon layer 32, said member 40 not beingconnected to the glass closure wafer 20, nor to the silicon oxide layer34, with said member 40 being separated from the remainder of thesilicon layer 32 by the gap 104.

In a first variant embodiment, the liquid inlet control member 100 ₁shown in FIG. 1A has a gap 104 ₁ in the form of an open ring such thatthe moving member is connected to the remainder of the silicon layer 32by an arm 41 situated to the left in FIG. 1A.

In a second variant embodiment, the liquid inlet control member 100 ₂shown in FIG. 1B comprises a gap 104 ₂ in the form of three angularsectors subtending an angle at the center of about 120° so that themoving member is connected to the remainder of the silicon layer 32 bythree arms 41 each situated between two of the above-mentioned angularsectors.

It will be understood that the member 40 is movable in a directionperpendicular to the main plane of the stack 30, i.e. upwards in FIG. 1,and orthogonally to the plane of the sheet in FIGS. 1A and 1B.Nevertheless, in the second variant embodiment, because of the threepoints attaching the moving member 40 to the silicon layer 32, it willbe understood that the moving member 40 is stiffer than it is in thefirst variant embodiment.

The very small thickness of this member 40 (less than 50 μm, andpreferably about 10 μm) makes it elastically movable in a directionextending transversely to the main plane of the stack 30 or of the glassclosure wafer 20, i.e. up and down as represented by the double-headedarrow in FIG. 1.

In FIG. 1, the member 100 forming an inlet valve is shown in its restposition, i.e. partially open. When liquid arrives via the inlet duct102, the moving member 40 lifts under the pressure of the liquid whichis then higher in the inlet duct 102 than in the cavity 38, such thatthe valve takes up its open position and enables the liquid to penetrateinto the zone 35, and to pass into the gap 104 so as to reach the cavity38.

This member 100 can be inserted in a fluid-flow assembly that is morecomplex, in which the member 100 constitutes an upstream liquid inletelement. Thus, it will be understood that the liquid present in thecavity 38 can be at a pressure which is higher than the pressure of theliquid in the inlet duct 102, thus enabling the member 100 to close bythe moving member moving downwards and coming into leaktight contactagainst the face of the silicon support wafer 36 facing towards thesilicon layer all around the second end 102 b of the duct 102.

The relative elasticity of the silicon layer 32 that is thinned-down inthe location of the cavity 38 (a single arm 41 in FIG. 1A, or three arms41 in FIG. 1B), makes it possible when the pressure of the liquid in thecavity 38 is no longer greater than the pressure of the liquid in theduct 102 for the member 40 to return to its initial position as shown inFIG. 1, i.e. a position in which the member 100 is partially closed.When the pressure of the liquid in the cavity 38 becomes higher than thepressure of the liquid in the duct 102, then the moving member 40 movesfully down and comes into leaktight contact against the support wafer36: the liquid inlet control member 100 is then closed.

It will be understood that this member 100 forms an inlet valve in whichthe valve body is constituted by the face of the moving member 40 facingtowards the silicon support wafer 36 and in which the seat of the valveis constituted by the region of the face of the silicon support wafer 36that faces towards the silicon layer 32 surrounding the second end 102 bof the duct 102.

In a second embodiment shown in FIGS. 2, 2A, and 2B, it is also possibleto establish prestress placing the liquid inlet control member 100′ inits closed position when the moving member 40 is in its rest position.

For this purpose, an isolated portion 106 of the moving member 40,situated in the middle of the arm 41, is of a thickness that is equal tothe initial thickness of the silicon layer 32. This portion 106 lies inregister with an element 110 situated on the face 20 a of the closurewafer 20 facing towards the stack, or on the free face of said portion106.

The element 110 is preferably taken from a layer of titanium depositedon the above-specified face 20 a of the closure wafer 20. This element110 pushes the isolated portion 106 downwards and forces the movingmember 40 into its closed position which then corresponds to its restposition. Nevertheless, the elasticity of the moving member 40 remainssufficient to enable it to be opened.

Thus, the portion 106 and said element 110 form bearing means placingsaid moving member 40, when in its rest position, in said closedposition.

FIGS. 3 and 3A relate to a third embodiment of the liquid inlet controlmember constituting the first aspect of the invention. In this case, theliquid inlet control member 100″ further comprises, compared with thefirst and second embodiments of the liquid inlet control member, asecond glass wafer 20′.

Thus, in this liquid inlet control member 100, the top closure wafer 20is a first closure wafer 20 of glass and the second glass wafer 20′forms a second closure wafer which is fixed to the face of the supportwafer 36 opposite from said first glass closure wafer 20.

This second closure wafer 20′ of glass is provided with a through duct102″a.

To move the body and the seat of the valve between the second closurewafer 20′ and the silicon support wafer 36, a moving portion 361 isformed throughout the thickness of the support wafer 36 in register withand in line with said cavity 38 of said moving member 40 and of saidduct 102″a. This moving portion 361 is situated close to but not inregister with said gap 104 ₂.

A matter-free annular volume 102″ is machined through the entirethickness of the support wafer 36 in register with said zone 35 that isentirely free from material in the layer of insulating material 34,thereby separating said moving portion 361 from the remainder of thesupport wafer 36 and thus forming said liquid inlet duct 102″ of thesupport wafer 36 which communicates with said gap 104 ₂.

The layer of insulating material 34 presents a connection zone 321surrounded by the zone 35 which is then annular, the connection zone 321securely connecting said moving portion 361 to said moving member 40,thus subjecting the moving portion 361 to the up or down movement of themoving member 40.

An annular valve element 370 made in an anti-adhesion material(preferably titanium) is situated on the face of the second closurewafer 20′ made of glass placed in register with said moving portion 361.

Because of this valve element 370, when said moving member 40 is asclose as possible to the support wafer 36 (a situation that is notshown), the face of the moving portion 361 facing towards the secondclosure wafer 20′ and the face of the valve element 370 facing towardsthe support wafer 36 are in leaktight contact, thus putting the liquidinlet control member 100″ into its closed position and preventing liquidfrom passing from the duct 102″a of the second closure wafer 20′ towardssaid liquid inlet duct 102″ of the support wafer 36.

In contrast, when there is no contact between the valve body (movingportion 361 in the example shown in FIGS. 3 and 3A) and the seat of thevalve (valve element 370 in the example shown in FIGS. 3 and 3A), thenthe liquid inlet control member 100″ is in its open position allowingliquid to pass from the duct 102″a of the second closure wafer 20′towards said liquid inlet duct 102″ of the support wafer 36, and fromthere towards the gap 104 ₂ and onto the cavity 38. This is thesituation shown in FIG. 3.

With reference to FIG. 3A, there can be seen the liquid inlet controlmember 100″ of FIG. 3 in plan view after the closure wafer 20 has beenremoved, and it can be seen that there is a high degree of similaritywith FIG. 1B since the moving member 40 is likewise connected by threearms 41 to the remainder of the silicon layer 32. The gap 104 ₂ is thuslikewise made up of three angular sectors each subtending an angle atthe center of about 120°, which sectors are annular in this case.

FIGS. 4 and 4A relate to a fourth embodiment of the liquid inlet controlmember constituting the second aspect of the invention. In this case, asfor the third embodiment shown in FIGS. 3 and 3A, the liquid inletcontrol member 100″′ further comprises a second glass wafer 20′, ascompared with the first and second embodiments of the liquid inletcontrol member.

This second glass wafer 20′ forms a second glass closure wafer which isfixed to the face of the support wafer 36 opposite from said first glassclosure wafer 20 and provided with a duct 102″a passing right throughit.

Like in the third embodiment of the liquid inlet control member as shownin FIGS. 3 and 3A, and likewise for the purpose of offsetting the bodyand the seat of the valve between the second closure wafer 20′ and thesilicon support wafer, a moving portion 361 is made throughout thethickness of the support wafer 36 of the liquid inlet control member100″′, in register with and in line with said cavity 38 and said movingmember 40.

This moving portion 361 is annular (see FIGS. 4 and 4A) and it isinitially defined by a first annular volume 102″′a that has no materialand that has been machined throughout the thickness of the support wafer36 in register with said zone 35 that is completely free from materialin the layer of insulating material 34 and said cavity 38. Thus, thefirst annular volume 102″′a separates said moving portion 361 from theremainder of the support wafer 36.

This annular moving portion 361 is subsequently likewise defined by asecond cylindrical volume 102″′ which is free from material and which ismachined through the entire thickness of the support wafer 36 at thelocation (middle) of the moving portion 361. This second material-freevolume 102″′ forms said liquid inlet duct 102″′ which communicates withthe gap 104 ₁ which is then situated in register with and in line withsaid liquid inlet duct 102″′.

Also in the same manner as for the third embodiment of the liquid inletcontrol member 100″ shown in FIGS. 3 and 3A, the layer of insulatingmaterial 34 of the liquid inlet control member 100″′ of this fourthembodiment presents a connection zone 321 surrounded by the zone 35 andconnecting said moving portion 361 securely to said moving member 40around the liquid inlet duct 102″′ and the gap 104 ₁. In this case, theconnection zone 321 and the zone 35 are annular and concentric.

This liquid inlet control member 100″′ further comprises an annularvalve element 370 made of an anti-adhesion material (preferablytitanium) situated on the face of the second glass closure wafer 20′placed facing said moving portion 361.

This annular valve element 370 surrounds said liquid inlet duct 102″′ ofthe support wafer 36, but does not surround the duct 102″a of theclosure wafer 20′ which opens out into the first annular volume 102″′athat is free from material in the support wafer 36.

Because of this valve element 370, when said moving member 40 is asclose as possible to the support wafer 36 (a situation which is notshown), the face of the moving portion 361 facing towards the secondclosure wafer 20′ and the face of the valve element 370 facing towardsthe support wafer 36 are in leaktight contact, thus putting the liquidinlet control member in its closed position. In this closed position ofthe liquid inlet control member 100″′, the liquid reaching the firstannular volume 102″′ from the duct 102″a of the second closure wafer 20′cannot penetrate into said liquid inlet duct 102″′ of the support wafer36: the liquid remains blocked in the first annular volume 102″′a of thesupport wafer 36.

In contrast, when there is no contact between the valve body (the movingportion 361 in the example shown in FIGS. 4 and 4A), and the valve seat(the valve element 370 in the example shown in FIGS. 4 and 4A), then theliquid inlet control member 100″′ is in its open position (see FIGS. 4and 4A) allowing liquid to pass from the duct 102″a of the secondclosure wafer 20′ towards the first annular volume 102″′a of the supportwafer 36, and then between the moving portion 361 and the valve element370 towards the liquid inlet duct 102″′ of the support wafer 36, andthen towards the gap 104 ₁ heading towards the cavity 38.

The valve elements 370 in the third and fourth embodiments of the liquidinlet control member (100″ and 100″′) could equally well be situated onthe face of said moving portion 361 that is placed facing the secondglass closure wafer 20′ and/or could equally well be made of some otheranti-adhesion material such as gold, silicon oxide, or silicon nitride.

Thus, the third and fourth embodiments of the liquid inlet controlmember as shown respectively in FIGS. 3 & 3A and 4 & 4A belong to asecond type of fluid-flow device in which a second glass wafer 20′ isneeded to offset the valve seat between said second glass wafer 20′ anda moving portion 361 of the support wafer 36 of the stack 30.

The operation of the liquid inlet control members 100″ and 100″′ isidentical to that of the liquid inlet control members 100 and 100′constituting the first and second embodiments (respectively shown inFIGS. 1, 1A, 1B, and in FIGS. 2, 2A, and 2B).

Compared with the method of manufacturing the liquid inlet controlmembers 100 and 100′ of the first and second embodiments (as shownrespectively in FIGS. 1, 1A, 1B, and FIGS. 2, 2A, and 2B), in order tomanufacture liquid inlet control members 100″ or 100″′ it suffices toprovide a second closure wafer 20′ on which an annular valve element 370is deposited, said valve element being made of an anti-adhesionmaterial, and then to connect it to the silicon wafer 36. These twosteps should be performed at the end of the manufacturing method, i.e.after the stack 30 has been subjected to treatment (in particular bymachining and/or structuring).

The presence of the valve element 370 in the liquid inlet controlmembers 100′ or 100″′ makes it possible to subject the moving member 40to pretension, since the presence of the thickness of the valve element370 offsets the moving member 40 a corresponding distance upwards (seeFIGS. 3 and 4) into the cavity 38.

Because of the micromachining techniques that can be used for processingthe stack 30, it is possible to control the volumes of the liquid inletducts 102″ or 102″′ of the support wafer 36 very accurately in order tominimize the dead volume represented by said ducts.

The liquid inlet control members 100″ or 100″′ as described above can beintegrated in a micropump as described below with reference to FIGS. 7and 8, so as to constitute an inlet valve.

FIG. 5 shows a second aspect of the fluid-flow device of the presentinvention corresponding to a member 400 for detecting liquid pressureand suitable for forming part of a more complex fluid-flow device thatis also capable of incorporating the above-described liquid inletcontrol member 100.

This liquid pressure detection member 400 comprises a glass closurewafer 20 placed over a stack 30 which has previously been machined so asto form various functional portions of said liquid pressure detectionmember 400.

This stack 30 comprises a silicon layer 32 surmounting a silicon oxidelayer 34, itself placed on a silicon support wafer 36.

This type of stack is commonly referred to as a silicon-on-insulatorstack (SOI) and is commercially available in the form of a wafer or aplate of the kind used in particular in the semiconductor electronicsindustry. As for the liquid inlet control member 100 described above,the roles of these three elements of the stack 30 lead to thicknessesthat are significantly different:

-   -   the silicon support wafer 36 acting as a rigid base preferably        presents thickness lying in the range 50 μm to 1000 μm, and        advantageously in the range 300 μm to 500 μm;    -   the silicon oxide layer 34 is for connecting the silicon support        wafer 36 to the silicon layer 32 while keeping a constant        spacing between them, while nevertheless being easily removed        from certain zones so its thickness must remain very small,        preferably in the range 0.1 μm to 2 μm, and advantageously in        the range 0.5 μm to 1 μm; and    -   the silicon layer 32 is designed to be machined through a        fraction only of its thickness (about half) in order to        co-operate with the glass closure wafer 20 to define a cavity        and a moving member; this silicon layer 32 which can be made of        single-crystal or polycrystalline silicon has initial thickness        that preferably lies in the range 1 μm to 100 μm, and        advantageously in the range 10 μm to 50 μm.

The stack 30 is machined using conventional techniques ofphotolithography and chemical etching in order to obtain the variousfunctional elements of said liquid pressure detector member 400, and inparticular a cavity 38 and moving member 40, prior to making theconnection between the glass closure wafer 20 and said stack 30. Thisconnection between the closure wafer 20 and the free face of the siliconlayer 32 is made in conventional manner by wafer bonding (anodic bondingwhen the closure wafer is made of glass), after which fixing is obtainedin the form of a leaktight connection.

This liquid pressure detector member 400 has a cavity 38 in which afluid flows, with the flow direction being represented by two horizontalarrows in FIG. 5. Under the pressure of this liquid, the moving member40 is capable of moving vertically towards or away from the siliconsupport wafer 36 (double-headed vertical arrow) until it comes intocontact with said silicon support wafer 36.

By way of example, the liquid flows through the cavity 38 from an inlet402 situated to the left of FIG. 5 to an outlet 404 situated to theright of FIG. 5.

In order to remove the material corresponding to the zone 35 of thesilicon oxide layer 34, a series of circular section ducts 412 is formedthrough the entire thickness of the silicon support wafer 36 in registerwith said zone 35 and the moving member 40.

As can be seen in FIGS. 5A and 5B, these ducts 412 are situated at equaldistances apart from one another in register with the entire zone 35from which silicon oxide is removed from the layer 34.

Another duct 412′ of cross-section in the form of a cylindrical wall,preferably an annular wall, is formed throughout the thickness of thesilicon support wafer 36 and surrounds the series of ducts 412. Thisduct 412′ serves to separate the remainder of the silicon support wafer36 from a bearing portion 414 in the form of a cylinder pierced by theducts 412 situated in register with the moving member 40 and connectedto an electrical connection.

In order to hold the bearing portion 414 secure with the stack 30, afraction 416 of the silicon oxide layer 34 is left intact on the edge ofthe bearing portion 414 beside the duct 412′. This fraction 416 connectsthe bearing portion 414 of the silicon layer 32 surrounding the movingmember 40, and thus constituting connection means.

In the variant embodiment shown in FIG. 5A, the duct 412′ and thefraction 416 are in the form of circularly cylindrical wall segments,whereas the ducts 412 are regularly distributed over a zone of circularshape.

In the variant embodiment shown in FIG. 5B, the ducts 412 are regularlydistributed over a zone of rectangular shape, the fraction 416 isconstituted by two fractions of semicircular shape situated along twoopposite sides of the above-specified rectangle so as to form two“lugs”. In FIG. 5B, the duct 412′ surrounds both the above-specifiedzone of rectangular shape and the two fractions 416, said duct 412′ thenbeing in the form of a wall of a rectangular section cylinder having twolugs, like a kind of four-leaf clover or a Greek cross.

This pressure detector member 400 is shaped in such a manner that whenthe liquid pressure exceeds a certain threshold in the cavity 38, themoving member 40 passes from its rest position or open position (asshown in FIG. 5) to an active position or closed position in which themoving member 40 comes into contact with the bearing portion 414 of thesilicon support wafer 36.

Under such circumstances, contact between the layer 32 (at the locationof the moving member 40) and the wafer 36 (at the location of thebearing portion 414), both of which are made of doped silicon forming asemiconductor that acts as an electrical conductor integrated in acapacitive circuit, gives rise to a sudden increase in capacitancebetween the electrical connections respectively connected to the layer32 and to the bearing portion 414 of the support wafer 36, and bydetecting such a sudden increase in capacitance it is possible todetermine whether a predetermined liquid pressure level has been reachedin the cavity 38.

Other variant embodiments can be envisaged, in particular the variantwhereby two electrodes forming two bearing portions are provided, saidelectrodes being separated from each other and from the remainder of thewafer 36.

This liquid pressure detector member 400 forms a liquid pressure sensorwhich operates in capacitive manner. Nevertheless, other types of sensormay be created using the member 400: a tunnel effect sensor; a Schotkycontact sensor; an inductive detector; an optical detector (e.g. using alaser diode which observes the bending of the moving member 40); or astrain gauge.

Such a liquid pressure detector member 400 is very useful in afluid-flow assembly since it makes it possible to detect when apredetermined pressure level has been reached in the cavity 38, as afunction of the pressure level which triggers contact between the movingmember 40 and the bearing portion 414.

Naturally, this pressure detector 400 is a differential sensor taking asits pressure reference the outside pressure that exists in the ducts 412and 412′ and in the zone 35 where there is no material.

FIG. 6 relates to a second embodiment of the liquid pressure detectormember constituting the second aspect of the invention. In this case,the liquid pressure detector member 400″′ further comprises, comparedwith the first embodiment of the liquid pressure detector member shownin FIGS. 5, 5A, and 5B, a second glass wafer 20′.

Thus, in this liquid pressure detector member 400″′, the top closurewafer 20 is a first glass closure wafer 20, and the second glass wafer20′ forms a second closure wafer which is fixed to the face of thesupport wafer 36 opposite from said first closure wafer 20 made ofglass.

The support wafer 36 is provided with a duct 422 passing right throughit.

In order to offset the electrical contact zone giving rise to thepressure threshold being detected so that it is shifted towards thesecond closure wafer 20′ made of glass, in the second embodiment of theliquid pressure detector member 400″′, the portion forming an islandseparated from the remainder of the support wafer 36 constitutes amoving portion 461.

The duct 422 is annular so as to separate the moving portion 461 fromthe remainder of the support wafer 36 and the layer of insulatingmaterial 34 presents a connection zone 321 surrounded by the zone 35connecting said moving portion 461 integrally with said moving member40.

In order to perform the functions of a pressure detector, this liquidpressure detector member 400″′ further comprises a first conductorelement 463 situated on the face of said moving portion 461 that facesthe second closure wafer 20′ of glass and a second conductor element 465situated on the face of the second closure wafer 20′ of glass placed inregister with said moving portion 461. Naturally, said first and secondconductor elements 463, 465 are suitable for coming into electricalcontact when said moving member 40 and said moving portion 461 which issecured thereto come close to the second closure wafer 20′ made ofglass.

As an alternative to this electrical contact, other detection methodscan be used: measurement can be capacitive, inductive, optical, or bystrain gauges placed on the moving member 40. In these other cases, thepresence and/or location of the first conductor element 463 and/or ofthe second conductor element 465 needs to be adapted to the detectiontechnique used.

As with the pressure detector 400 described with reference to FIGS. 5,5A, and 5B, the liquid pressure detector 400″′ makes it possible toidentify a determined pressure threshold relative to the outsidepressure because of the increasing deformation of the moving member 40due to the increase in the liquid pressure inside the pumping chamber.

Thus, the second embodiment of the pressure detector member as shown inFIG. 6 belongs to a second type of fluid-flow device in which a secondglass wafer 20′ is necessary in order to be able to offset electricalcontact between said second glass wafer 20′ and a moving portion 461 ofthe moving wafer 36 of the stack 30.

The pressure detector and control members 400 and 400″′ described abovecan be integrated in a micropump of the kind described below withreference to FIGS. 7 and 8, as an inlet valve.

Compared with the method of manufacturing the pressure detection controlmember 400 of the first embodiment (FIGS. 5, 5A, and 5B), in order tomanufacture the pressure detection control member 400″′ it suffices toprovide a second closure wafer 20′ on which a second conductor element465 of electrically conductive material is deposited, and to connect itto the silicon support wafer 36. These two steps are performed at theend of the manufacturing process, i.e. after treating (in particular bymachining and/or structuring) the stack 30 and after providing the faceof the moving portion 461 facing away from the moving member 40 with afirst conductor element 463 made of an electrically conductive material.Naturally, provision must be made to connect the first and secondelectrically conductive elements 463 and 465 to the circuit of thedetector system.

It should be observed that the term “duct” is used for the channels orvolumes 412, 412′, and 422 in the two embodiments 400 and 400″′ of thepressure detector, even though they are not designed to have fluidflowing through them while this fluid-flow member is in operation.

The first and second aspects of the fluid-flow device of the presentinvention as described above with reference to FIGS. 1 to 6 implementdifferent functions relating to the passing of liquid in a fluid-flowdevice and are of analogous simple structure suitable for beingimplemented using a manufacturing method that is very simple toimplement.

In addition, this method of manufacturing the various members 100, 100″,100″′, 400 and 400″′ as described above presents high degrees ofsimilarity such that these various fluid-flow members 100, 100″, 100″′,400, and 400″′ can easily be located in a single fluid-flow assembly.

An example of such integration is described below with reference toFIGS. 7 to 15. The common steps of the method of manufacturing themembers 100, 100″, 100″′, 400, and 400″′ are stated at the beginning ofthe present description when specifying a method of manufacturing afluid-flow device, which method presents adaptations in order to makeeach specific member 100, 100″, 100″′, 400, and 400″′, as specifiedbelow.

The method of manufacturing the liquid inlet control member 100 as shownin FIG. 1 comprises the following steps:

a) a stack 30 is provided that comprises a support wafer 36, preferablymade of silicon, a silicon oxide layer 34 covering at least part of thesupport wafer 36, and a layer of (single-crystal or polycrystalline)silicon 32 covering the silicon oxide layer 34 and presenting a freeface opposite from its face covering said layer 34 of silicon oxide;

b) the cavity 38 is machined from the free face of the silicon layer 32by photolithography and chemical etching;

c) the gap 104 is machined from the free face of the silicon layer 32 byphotolithography and chemical etching through the entire thickness ofthe silicon layer 32 until the layer 34 of silicon oxide is reached;

d) from the other side of the stack 30, the liquid inlet duct 102passing right through the support wafer 36 is machined byphotolithography and chemical etching;

e) the silicon oxide layer 34 is chemically etched through the duct 102and the gap 104 so as to create the zone 35 that is free from materialin the silicon oxide layer 34 so that the zone of the silicon layer 32situated facing said zone 35 is freed of the layer 34 of silicon oxide,thus forming the moving member 40, which member remains connected to thesilicon layer 32 by the arm(s) 41;

f) the closure wafer 20 is provided; and

g) physicochemical means are used to connect the closure wafer 20 inleaktight manner to the surface of the silicon layer 32 that has notbeen subjected to machining, preferably by a wafer bonding technique.

When the closure wafer 20 is made of glass, the above-mentioned waferbonding technique consists in anodic bonding. If the closure wafer ismade of silicon, then direct bonding enables a leaktight connection tobe made with the silicon layer 32.

It will thus be understood that the micromachining processing of thestack 30 is performed in independent manner for each of its faces suchthat the group of steps b) and c), and the group of steps d) and e) canbe performed one before the other as described above, or one after theother.

The liquid pressure detector member 400 shown in FIG. 5 and representingthe second aspect of the present invention is made using a method thatcomprises the following steps:

a) a stack 30 is provided comprising a support wafer 36 that ispreferably made of silicon, a silicon oxide layer 34 covering at leastpart of the support wafer 36, and a layer 32 of (single-crystal orpolycrystalline) silicon covering the layer 34 and presenting a freeface opposite from a face covering the silicon oxide layer 34;

b) a cavity 38 is machined from the free face of the silicon layer 32 byphotolithography and chemical etching;

c) from the other side of the stack 30, the ducts 412 and 412′ passingright through the support wafer 36 are machined from the other side ofthe stack 30;

d) the silicon oxide layer 34 is subjected to chemical etching via theducts 412 and 412′ so as to form the zone 35 in the silicon oxide layer34 that is free from material, while leaving silicon oxide in thefraction 416 so as to release the moving member 40 from the siliconoxide layer 34;

e) the closure wafer 20 is provided; and

f) a physicochemical method is used for connecting the closure wafer 20in leaktight manner to the surface of the silicon layer 32 that has notbeen subjected to machining, preferably using a wafer bonding technique.

Whether for one of the liquid inlet control members 100, 100″, 100″′, orfor one of the liquid pressure detection members 400, 400″′, it will beunderstood that the machining of the cavity 38 situated between thesilicon layer 32 and the closure wafer 20 can be performed equally wellby machining the layer 32 and the wafer 20 or by machining the wafer 20alone.

Reference is now made to FIGS. 7 to 9 showing a micropump 500 forming afluid-flow assembly integrating a liquid inlet control member 100, apumping portion 502, a pressure detection member 400, and a liquidoutlet control member 200.

Preferably, in addition to the glass closure wafer 20 and the stack 30,the micropump is provided with an additional glass closure wafer 20′bonded to the face of the support wafer 36 opposite from its facecarrying the glass closure wafer 20, i.e. in the bottom portions ofFIGS. 7 and 8.

It will thus be understood that the closure wafer 20 constitutes a firstglass closure wafer and that the additional closure wafer 20′constitutes a second glass closure wafer fixed on the face of thesupport wafer 36 that is opposite from the face carrying the first glassclosure wafer 20.

As described in greater detail below, the glass closure wafer 20 servesnot only to close the liquid-filled space of the micropump in leaktightmanner, but also as an abutment during the up stroke of the pumpdiaphragm 506. In order to prevent sticking or a suction cup effectbetween the pump diaphragm and the closure wafer 20, elements 510 madeof an anti-adhesion material are situated on the face 20 a of theclosure wafer 20 that faces towards the stack.

These elements 510 are preferably derived from a layer of titaniumplaced on the above-specified face 20 a of the closure wafer 20. Theseelements 510 form mutually separate projections which enable liquid toflow between them while preventing the pump diaphragm 506 from adheringto the closure wafer 20.

It should be observed that these elements 510 could equally well besituated on the silicon layer 32, i.e. in particular on the free face ofthe diaphragm 506.

The closure wafer 20′ also serves as an abutment element, in this casefor the down stroke of the diaphragm 506 by contact being establishedbetween the wafer 20′ and the moving pump portion 514. Combining thesetwo abutments (wafers 20 and 20′) makes it possible to control thevertical stroke amplitude of the diaphragm 506 and to ensure that thevolume pumped is accurate.

In order to ensure that the part 514 remains free to move, ananti-adhesion layer 520 is provided (see FIGS. 7 and 8) on theadditional closure wafer 20′ facing towards the stack 30. This layer 520is in the form of a ring and is positioned on the edge of an opening 522passing through the additional closure wafer 20′.

The layer 520 is preferably made of titanium and thus prevents themoving pump part 514 from sticking to the additional closure wafer 20′while the stack 30 is being bonded to the additional closure wafer 20′.

Naturally, the layer 520 could equally well be deposited on the face ofthe moving pump part 514 that faces away from the stack 30.

For the elements 110, 510, and 520, titanium can advantageously bereplaced by some other anti-adhesion material such as gold, siliconoxide, or silicon nitride.

In the upstream portion of the micropump 500, there can be found theliquid inlet control member 100, the liquid inlet duct 102 beingextended through the additional closure wafer 20′ of glass by a liquidinlet duct 102′ having an inlet where the liquid that is to be deliveredby the micropump 500 arrives.

This liquid inlet control member 100 comprises a zone 35 ₁ of thesilicon oxide layer 34 that is free from material, the cavity 38 ₁, andthe gap 104 which define the moving member 40 ₁. The liquid inletcontrol member 100 is shown in its rest position in FIGS. 7 and 8.

Between the liquid inlet control member 100 and a pressure detector 400,the micropump 500 comprises the pumping portion 502 provided with a pumpchamber 504 situated in the extension to the cavity 38 ₁ and definedbetween the glass closure wafer 20 and the silicon layer 32 whose facefacing towards the glass closure wafer 20 has been machined.

A pump diaphragm 506 in the form of a disk is situated in the siliconlayer 32 in register firstly with the pump chamber 504 and secondly withan annular volume 508 that is free from material machined in the supportwafer 36, said annular volume 508 free from material being extended inthe silicon layer 34 by a material-free zone 535.

This volume 508 serves to separate the remainder of the silicon supportwafer 36 from a moving pump part 514 in the form of a solid cylinder ofcircular section situated in register with the pump diaphragm 506 towhich it is connected by a fraction 516 of the silicon oxide layer 34that has been left intact.

Since the volume 508 is isolated from the remainder of the support wafer36, it is possible advantageously to integrate in the moving pump part514 at least one liquid pressure detection member, e.g. in the form ofone or more liquid pressure detectors operating in similar manner tothat of FIGS. 5, 5A, and 5B.

Such a variant embodiment is shown in FIG. 16A which shows a pumpingportion 502′ fitted with eight liquid pressure detectors 400′ regularlydistributed angularly in a moving pump part 514′ pierced right throughby eight series of ducts 512′. These eight series of ducts 512′ areisolated from one another by a fraction 516′ of the silicon oxide layer34 that is left intact except for respective zones in each of thedetectors 400′ to interconnect the corresponding series of ducts 512′.

Naturally, a pumping portion 502′ could be provided that is fitted withat least two liquid pressure detectors 400′ each forming a liquidpressure detection member and regularly spaced apart angularly in saidmoving pump part 514′ which is pierced right through by at least twoseries of ducts 512′.

Another variant embodiment of the pumping portion is shown in FIG. 16Bunder numerical reference 502″. In this case, the eight series of ducts512′ of FIG. 16A are accompanied by other ducts 512′ so that all ofthese ducts cover an annular zone that is to form a single annularliquid pressure detector 400″. In this other variant embodiment, thefraction of the silicon oxide layer 34 that is left intact is restrictedto a first annular fraction 516″a situated substantially at the edge ofthe moving pump part 514′ and to a second fraction 516″b situatedessentially in the center of the moving pump part 514′.

The moving pump part 514′ is also pierced right through, preferably inits center, by a passage 540 suitable for receiving a control rod (notshown) having one end fixed to the diaphragm 506 and having its otherend projecting out from the opening 522 to form a handle. This handleallows a user, where necessary, to pull the diaphragm 506 by means ofsaid rod in order to move it away from the closure wafer 20. A series ofsuch actions can be performed to develop high levels of suction insuccession in the pump chamber 504, or else to accelerate the operationof the micropump. It should be observed that the presence of the passage540 and of the rod is independent of the presence of a pressuredetection member in the moving pump part 514.

It should also be observed that the micropump control means situated inregister with the pump diaphragm 506 and generically referred to as anactuator can be integrated directly in the micropump by being fixed onthe face of the glass wafer 20′ facing away from the stack and by beingfixed to the moving pump part 514, or can be external to the micropump,being connected indirectly to the pump diaphragm 506.

These control means may, in particular, be of the type operatingpiezoelectrically, electromagnetically, or pneumatically.

Downstream from the pumping portion 502, the micropump 500 shown inFIGS. 7 and 8 includes the liquid pressure detector 400 described withreference to FIGS. 5, 5A, and 5B, the passage 412 being connected toexternal pressure via a duct 413′ passing through the additional glassclosure wafer 20′. In addition, there can be seen the other componentelements of the liquid pressure detection member 400, specifically thezone 35 ₄ of the silicon oxide layer 34 that is free from material, andthe cavity 38 ₄ which defines the moving member 40 ₄ between a liquidinlet 402 and a liquid outlet 404.

In FIGS. 7 and 8, the liquid pressure detection member 400 is shown inits rest or open position, i.e. with a moving member 40 ₄ that is not incontact with the bearing portion 414. It should be observed that theelectrical connections to the bearing portion 414 and to the siliconlayer 32 are not shown.

It will thus be understood that the pressure detector servers to verifythat the micropump is operating properly by detecting the transientincrease in liquid pressure on each stroke of the pump that results fromthe pump diaphragm 506 deflecting (an increase in pressure correspondingto the diaphragm 506 moving upwards in FIGS. 7 and 8, and vice versa).It is possible to detect either that pumping is not taking place becausethere is no increase in pressure, or else that there is a blockagedownstream because of the high pressure lasting for an excessively longperiod of time.

In the furthest downstream portion of the micropump 500, there is aliquid outlet control member 200 shown on a larger scale in FIG. 17.

This liquid outlet control member 200 forms a non-return check valvethrough which the liquid is delivered via a liquid outlet duct 204through the silicon support wafer 36 and extended through the additionalglass closure wafer 20′ by a liquid outlet duct 204′.

The other component elements of this liquid outlet control member 200are a zone 35 ₂ that is free from material in the silicon oxide layer34, a moving member 40 ₂ defined by the cavity 38 ₂, said moving member40 ₂ having an annular fraction 206 forming the valve body with thesecond end thereof coming into contact with an anti-adhesive layer 210situated on the closure wafer 20, the annular fraction 206 being piecedby an orifice 208. In FIGS. 7 and 8, the outlet control member 200 isshown in the closed position.

The liquid outlet control member 200 shown on a larger scale in FIG. 17,and its variant embodiment 300 shown in FIG. 18 are made using the sameelements as the member 100 of FIG. 1.

As can be seen in FIG. 17, the liquid outlet control member 200 presentsa liquid inlet 202 in the cavity 38 ₂ and a liquid outlet duct 204machined through the entire thickness of the silicon support stack 36 inregister with the cavity 38.

The zone 35 ₂ of the silicon oxide layer 34 that is free from materialis located at least in line with the liquid outlet duct 204 and extendsslightly beyond it all around said duct 204.

When making the cavity 38 by machining the silicon layer 32, the movingmember 40 is formed with a fraction 206 extending over substantially theentire initial thickness of the silicon layer 32 and presenting a closedoutline, preferably an annular outline. This fraction 206 extends from afirst end 206 a facing the zone 35 ₂ of the layer of insulating material34 to a second end 206 b close to the face 20 a of the closure wafer 20facing towards the stack 30.

This fraction 206 is in the form of a preferably annular cylindricalsleeve and it surrounds an orifice 208 situated in line with the zone 35₂ and the duct 204 with which the orifice 208 is in fluid communication.

In this liquid outlet control member 200, the moving member 40 liesacross substantially the entire section of the liquid outlet duct 204.

The valve seat is constituted by an anti-adhesion element 210,preferably made of titanium, situated on the face 20 a of the glassclosure wafer 20 facing towards the moving member 40 ₂. Thisanti-adhesion element 210 is similar in shape to the fraction 206, andis thus preferably annular. This anti-adhesion element 210 could also besituated on the second end 206 b of the fraction 206 and could equallywell be made of some other anti-adhesion material such as gold, siliconoxide, or silicon nitride.

The valve body is constituted by the second end 206 b of the annularfraction 206 whose first end 206 a faces towards the silicon supportwafer 36 and is adjacent to the liquid outlet duct 204.

In order to minimize the contact areas of the valve, the second end 206b of the annular fraction 206 is of small thickness, the orifice 208being larger at this level.

In FIG. 17, the liquid outlet control member 200 is shown in the restposition corresponding to a closed position, the liquid arriving via theinlet 202 being prevented from penetrating into the orifice 208 by thefraction 206 whose second end 206 b is in leaktight contact with saidanti-adhesion element 210.

Sufficient liquid pressure in the liquid inlet 202 exerts force on themoving member making it possible, if the liquid pressure in the outletduct 204 is less than the liquid inlet pressure, to open the valve bymoving the moving member 40 ₂ towards the silicon support wafer 36(configuration not shown). In this open position, the liquid can passover the second end 206 b of the fraction 206 which has been moved awayfrom said anti-adhesion element 210 and the closure wafer 20, so as topenetrate into the orifice 208 which is in direct fluid communicationwith the liquid outlet duct 204.

It will also be understood that said anti-adhesion element 210 makes itpossible to prevent the valve body formed by the second end 206 b of thefraction 206 sticking against the valve seat (the face of saidanti-adhesion element 210 that faces towards the stack 30).

In addition, it will be understood that said anti-adhesion element 210makes it possible by an initial elastic displacement of the movingmember 40 ₂ to establish pretension in the liquid outlet control member200 so that the valve remains closed in its rest position and for liquidpressure that does not exceed a predetermined threshold.

It is also by means of a resilient return phenomenon whereby, when theliquid pressure in the inlet 202 is less than or equal to the liquidpressure in the outlet duct 204, the control member 200 returns to itsclosed position shown in FIG. 17, the leaktight contact between thesecond end 206 b of the fraction 206 and said anti-adhesion element 210preventing any subsequent flow of liquid from the liquid inlet 202 tothe orifice 208.

FIG. 18 shows a variant embodiment corresponding to a liquid outletcontrol member 300 in which the liquid inlet 302 is made in the cavity38 while the liquid outlet duct 304 passes right through the glassclosure wafer 20.

The moving member 40 of this liquid outlet control member 300 is verysimilar in shape to the moving member 40 of FIG. 17: it has an annularfraction 306 similar to the fraction 206, however it does not have anorifice such as the orifice 208.

In this case, the annular fraction 306 still acts as the valve body bymaking leaktight contact (in the closed position as shown in FIG. 18)between the second end 306 b of the annular fraction 306 facing towardsthe closure wafer and facing an anti-adhesion element 310 that itselffaces the stack 30.

In this case, in order to enable the moving member 40 to movevertically, as represented by the double-headed arrow in FIG. 18, thezone 35 of the silicon oxide layer 34 that is free of material extendsin register with all the moving member 40.

In addition, access to the silicon oxide layer 34 is provided from thefree face of the silicon support stack 36 in order to remove siliconoxide from the zone 35 by means of a passage 312 that passes rightthrough the silicon support stack 36. This passage 312 preferably, butnot necessarily, presents a cylindrical shape, being circular incross-section as shown in FIG. 18.

The micropump 500 can be used in numerous applications, in particular asa pump for medical use for continuously delivering a liquid medicine.

Because of its very small dimensions, such a pump may be of the“implantable” type, i.e. it may be placed beneath the skin of a patient,or it may be of the external type, and be connected via its inletcontrol member 100 to the patient's blood circulation system via aninlet port passing through the skin.

FIGS. 10 to 15 show various steps in manufacturing the micropump 500comprising in particular steps of manufacturing the members 100, 200,and 400, and the pumping portion 502, these steps being performedsimultaneously.

In these various manufacturing steps, a distinction is drawn between“machining” which is used for machining that is intended to vary thethickness of a wafer or certain zones of a wafer, and the term“structuring” which is used for machining in the sense of conserving thematerial of a layer in certain zones and removing all of the material ofthat layer from other zones.

The method of manufacturing the micropump 500 comprises the followingsteps:

a) a stack 30 is provided comprising a support wafer 36 preferably madeof silicon, a layer of insulating material 34 preferably made of siliconoxide and covering at least part of the support wafer 36, and a layer 32of (single-crystal or polycrystalline) silicon covering the layer 34 ofinsulating material and presenting a free face opposite from a facecovering the layer 34 of insulating material;

b) by means of photolithography and chemical etching from the free faceof the support wafer 36, the following are machined: the liquid inletduct 102 of the inlet control member 100, the annular volume 508, theducts 412 and 412′ of the pressure detector 400, and the liquid outletduct of the liquid outlet control member 200, these ducts or annularvolume passing right through the support wafer 36 (FIG. 11);

c) by means of photolithography and chemical etching (hydrofluoric acidor BHF-buffered hydrofluoric acid) from the other side of the stack 30,i.e. from the free face of the silicon layer 32, the following aremachined: the gap 104 and the cavity 38 ₁ of the inlet control member100, the pump chamber 504, the cavity 38 ₄ of the pressure detector 400,the cavity 38 ₂, and the orifice 308 of the liquid outlet control member200 (FIGS. 9 to 14);

d) the silicon oxide layer 34 is subjected to chemical etching via theliquid inlet duct 102 of the inlet control member 100, via the annularvolume 508, via the ducts 412 and 412′ of the pressure detector 400, andvia the liquid outlet duct 204 of the liquid outlet control member 200so as to form the zones 35 ₁, 535, 35 ₄ and 35 ₂ of the silicon oxidelayer 34 that are free from material, thus making it possible to releasethe following respectively from the silicon oxide layer 34: the movingmember 40 ₁, the diaphragm 506, the moving member 40 ₄, and the movingmember 40 ₂ (FIG. 15);

e) the first closure wafer 20 is provided; and

f) a layer of anti-adhesion material, preferably titanium, is depositedby a physicochemical method on a face 20 a of the first closure wafer 20that is to be connected to said stack 30;

g) the layer of anti-adhesion material is structured as to form saidelements 510 and said anti-adhesion layer 210;

h) the second closure wafer 20′ is provided;

i) a layer of anti-adhesion material, preferably titanium, is depositedby a physicochemical method on a face of the second closure wafer 20′that is to be connected to said stack 30;

j) the layer of anti-adhesion material is structured so as to form saidring-shaped layer 520;

k) the first closure wafer 20 is connected in leaktight manner by aphysicochemical method to the surface of the silicon layer 32 which hasnot been machined, preferably by wafer bonding; and

l) the second closure wafer 20′ is connected in leaktight manner by aphysicochemical method to the surface of the support wafer 36 that hasnot been machined, preferably by wafer bonding.

It will be understood that the micropump 500 as obtained in this way ismanufactured in a manner that is very simple and that presents veryregular thickness characteristics for all of its component portionsbecause they are made from the same initial stack 30, therebyguaranteeing in particular that the pumping dead volume is very small.

As an illustration of the simplification provided by the manufacturingmethod, in order to make a prior art micropump it is necessary to useabout twelve photolithographic masks in order to make and machine all ofthe various layers, whereas using the above-described method of thepresent invention, about five masks suffices.

1. A method of manufacturing a fluid-flow device, the method comprisingthe following steps: providing a stack (30) comprising a support wafer(36), one layer of insulating material (34) covering directly at leastpart of said support wafer (36), and one layer of single-crystal orpolycrystalline silicon (32); covering directly said layer of insulatingmaterial (34) and presenting a free face; providing at least one closurewafer (20); using photolithography and chemical etching to machine acavity (38) from said closure wafer (20) and/or from the free face ofsaid silicon layer (32); using photolithography and chemical etching tomachine at least one duct (102) passing right through said support wafer(36); chemically etching said layer of insulating material (34) at leastvia said duct (102) such that a zone (35) of said silicon layer (32) isfreed from said layer of insulating material (34), thereby forming amoving member (40) in said silicon layer (32), said moving member (40)remaining connected to the silicon layer (32) and facing said freed zone(35); using a physicochemical method to connect said closure wafer (20)in leaktight manner directly to said free face of silicon layer (32)thereby said moving member (40) facing said cavity (38).
 2. Methodaccording to claim 1, wherein said support wafer (36) is made ofsilicon.
 3. Method according to claim 1, wherein said insulatingmaterial (34) is made of silicon oxide.
 4. Method according to claim 1,wherein said physicochemical method is a wafer bonding technique.
 5. Amethod of manufacturing a liquid inlet control member 100, the methodcomprising the steps of: providing a stack (30) that comprises a supportwafer (36), one insulating material layer 34 covering directly at leastpart of the support wafer (36), and one layer of silicon (32) coveringdirectly the insulating material layer (34) and presenting a gee faceopposite from its face covering said layer (34) of insulating material;machining a cavity (38) from the free face of the silicon layer (32) byphotolithography and chemical etching; machining a gap (104) from thefree face of the silicon layer (32) by photolithography and chemicaletching through the entire thickness of the silicon layer (32) until thelayer (34) of insulating material is reached; from the other side of thestack (30), machining a liquid inlet duct (102) passing right throughthe support wafer (36) by photolithography and chemical etching;chemically etching the insulating material layer (34) through the duct(102) and the gap (104) so as to create a zone (35) that is freed frommaterial in the insulating material layer (34) so that the zone of thesilicon layer (32) situated facing said zone (35) is freed of the layer(34) of insulating material, thus forming the moving member (40) in saidsilicon layer (32), which moving member (40) remains connected to thesilicon layer (32) by arm(s) (41) and faces said freed zone (35);providing a closure wafer (20); and using physicochemical means toconnect the closure wafer (20) in leaktight manner directly to said freeface of the silicon layer (32).
 6. Method according to claim 5, whereinsaid support wafer (36) is made of silicon.
 7. Method according to claim5, wherein said insulating material (34) is made of silicon oxide. 8.Method according to claim 5, wherein said physicochemical method is awafer bonding technique.
 9. A method of manufacturing a liquid pressuredetector member 400, the method comprising the steps of: providing astack (30) comprising a support wafer (36), one insulating materiallayer (34) covering directly at least part of the support wafer (36),and one layer (32) of silicon covering directly the insulating materiallayer (34) and presenting a free face opposite from a face covering theinsulating material layer (34); machining a cavity (38) from the freeface of the silicon layer (32) by photolithography and chemical etching;from the other side of the stack (30), machining at least two ducts(412) and (412′) passing right through the support wafer (36);subjecting the insulating material layer (34) to chemical etching viathe ducts (412) and (412′) so as to form a zone (35) in the insulatingmaterial layer (34) that is free from material, while leaving insulatingmaterial in the fraction (416) so as to release a moving member (40)from the insulating material layer (34), said moving member (40)remaining connected to the silicon layer 32 and facing said freed zone;providing a closure wafer (20), and using a physicochemical method forconnecting the closure wafer (20) in leaktight manner directly to saidfreed face of the silicon layer (32).
 10. Method according to claim 9,wherein said support wafer (36) is made of silicon.
 11. Method accordingto claim 9, wherein said insulating material (34) is made of siliconoxide.
 12. Method according to claim 9, wherein said physicochemicalmethod is a wafer bonding technique.
 13. A method of manufacturing amicropump (500), the method comprising the steps of: providing a stack(30) comprising a support wafer (36), one layer of insulating material(34) and covering directly at least part of the support wafer (36), andone layer (32) of silicon covering directly the layer (34) of insulatingmaterial and presenting a free face opposite a face covering the layer(34) of insulating material; by means of photolithography and chemicaletching from the free face of the support wafer (36), machining thefollowing: one liquid inlet duct (102) of the inlet control member(100), an annular volume (508), at least two ducts (412) and (412′) of apressure detector (400), and a liquid outlet duct of a liquid outletcontrol member (200), these ducts or annular volume passing rightthrough the support wafer (36); by means of photolithography andchemical etching, from the other side of the stack (30), that is, fromthe free face of the silicon layer (32), machining the following: a gap(104) and a first cavity (381) of the inlet control member (100), a pumpchamber (504), a second cavity (384) of the pressure detector (400), athird cavity (382), and an orifice (308) of the liquid outlet controlmember (200); subjecting the insulating material layer (34) to chemicaletching via the liquid inlet duct (102) of the inlet control member(100), via the annular volume (508), via the ducts (412) and (412′) ofthe pressure detector (400), and via the liquid outlet duct (204) of theliquid outlet control member (200) so as to form zones (351), (535),(354) and (352) of the insulating material layer (34) that are free frommaterial, thus making it possible to release the following movingmembers respectively from the insulating material layer (34): a firstmoving member (401), a diaphragm (506), a second moving member (404),and a third moving member (402), said moving members remaining connectedto the silicon layer (32) and respectively facing one of freed zones(351), (535), (354) and (352) of the insulating material layer (34);providing a first closure wafer (20); depositing a layer ofanti-adhesion material by a physicochemical method on a face (20 a) ofthe first closure wafer (20) that is to be connected to said stack (30),the layer of anti-adhesion material being structured as to form elements(510) and an anti-adhesion layer (210); providing a second closure wafer(20′) depositing another layer of anti-adhesion material by aphysicochemical method on a face of the second closure wafer (20′) thatis to be connected to said stack (30), said layer of anti-adhesionmaterial being structured so as to form a ring-shaped layer (520);directly connecting the first closure wafer (20) in leaktight manner bya physicochemical method to the free face of the silicon layer (32); andconnecting the second closure wafer (20′) in leaktight manner by aphysicochemical method to the surface of the support wafer (36) that isnot covered by the layer of insulating material (34).
 14. Methodaccording to claim 13, wherein said support wafer (36) is made ofsilicon.
 15. Method according to claim 13, wherein said insulatingmaterial (34) is made of silicon oxide.
 16. Method according to claim13, wherein said physicochemical method is a wafer bonding technique.17. Method according to claim 13, wherein said anti-adhesion material ismade of titanium.